This invention relates to ammunition and to discarding sabot projectiles. There is a need for a means for retaining the projectile core in the sabot so that the projectile core is not forced out of the sabot by the debulleting loads during ramming of the projectile in the gun. For automatic weapons the debulleting load is frequently in excess of 3000 g's. If a retainer were not used the relatively heavy core could move forward during ramming and separate from the relatively light sabot of the projectile possibly exiting the gun barrel before the round was fired. To prevent this a common conventional technique is using a split retaining ring with a matching groove in the sabot body and penetrator. During projectile spin-up as it travels down the barrel the split retaining ring centrifuges out of a groove in the penetrator and into a deeper outer groove in the sabot and no longer prevents the penetrator from separating from the sabot during normal separation. The problem with this design is that it requires the machining of an internal groove in the sabot, usually at the base of the sabot internal cavity which is difficult and expensive. Also, a matching groove must be machined in the penetrator outside diameter. This weakens the penetrator by virtue of creating a stress riser and reduces the penetrating capability of the penetrator as compared to a penetrator without the groove.
The invention has sought to overcome this problem by the use of either "fingers" that are crimped onto the projectile core nose section or an "O" ring that is in frictional contact with the core. As the core tries to move forward it applies a frictional load to the "O" ring, wedging it between the core and sabot body preventing forward movement. During spin-up the "O" ring moves outward into the groove since no wedging or frictional loads are applied, but rather the inertia of the projectile core forces it backward relative to the sabot upon firing and during spin-up.